This invention relates to a method and apparatus for treating a waste stream containing volatile organic compounds ("VOC").
Treatment of waste in industrial facilities causes a multitude of environmental and economic problems. Over the years, increasingly strict governmental pollution guidelines, as well as increased costs of waste disposal, have led to escalating concern in waste treatment. The difficulty in disposing of gaseous waste materials is increased when the waste includes dilute concentrations of VOCs. Under these circumstances, it is desireable to first concentrate the VOCs through the use of carbon, zeolite or other adsorption media.
Heated desorption gases are thereafter used to remove VOCs from the adsorption media and create a VOC laden effluent. The effluent is then oxidized, or combusted, to destroy the VOCs prior to discharge into the atmosphere.
Problems in the treatment of VOC waste streams, such as that of paint spray booth facilities, arise in the context of trying to simultaneously maximize the thermal efficiency of the waste treatment process and attempting to minimize the use, complexity and cost of the system. Some prior art systems have employed regenerative thermal units to oxidize VOCs. However, VOC abatement systems which currently use regenerative thermal units for oxidizing VOC require additional equipment, such as a "desorption heater" for providing the heated desorption air. Additionally, the pressure drop experienced across the regenerative thermal unit requires larger motors and fans, thus increasing the initial and operational costs of the system.
Alternatively, prior art VOC abatement systems have utilized a recuperative thermal oxidizer in combination with a heat exchanger for heating desorption gasses. However, these systems sacrifice thermal efficiency of the system. Typically, recuperative units will achieve no more than 70% thermal efficiency, whereas their regenerative thermal oxidizer counterparts achieve 90% to 95% efficiency.
No prior art system has been developed for oxidizing VOCs which incorporates the thermal efficiency of regenerative thermal oxidizers while maintaining the design simplicity and cost efficiency of recuperative thermal oxidizers. It is, therefore, desirable to provide a method and apparatus which effectively and economically oxidizes VOC waste streams. It is also desirable to provide a method and apparatus which oxidizes VOC waste streams while utilizing a design with minimal complexity and weight.